package requestbudget

import (
	"context"
	"errors"
	"net/http"
	"net/http/httptest"
	"sync/atomic"
	"testing"
	"time"
)

func TestGraphExecutionRefusesFourthSendAndScopeChanges(t *testing.T) {
	for _, mismatch := range []string{"limit", "model", "phase"} {
		t.Run(mismatch, func(t *testing.T) {
			ctx, guard, cancel, err := BindGraphExecution(context.Background(), "spent-receipt", "model")
			if err != nil {
				t.Fatal(err)
			}
			defer cancel()
			ctx = WithModel(ctx, "model")
			if mismatch == "model" {
				ctx = WithModel(ctx, "changed")
			}
			if mismatch == "phase" {
				ctx = WithPhase(ctx, "changed")
			}
			sends := 0
			transport := Transport{Base: roundTripFunc(func(*http.Request) (*http.Response, error) {
				sends++
				return nil, errors.New("provider failure")
			})}
			for i := 0; i < 4; i++ {
				req, _ := http.NewRequestWithContext(ctx, http.MethodPost, "http://local.test", nil)
				_, _ = transport.RoundTrip(req)
			}
			want := 0
			if mismatch == "limit" {
				want = 3
			}
			if sends != want || guard.Reservations() != want || !errors.Is(guard.Check(ctx), ErrStopped) {
				t.Fatalf("sends=%d reserved=%d stop=%v", sends, guard.Reservations(), guard.Check(ctx))
			}
		})
	}
}

func TestGraphExecutionCancelsBlockedHTTPAtInheritedDeadline(t *testing.T) {
	var sends atomic.Int32
	arrived := make(chan struct{})
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		sends.Add(1)
		close(arrived)
		<-r.Context().Done()
	}))
	defer server.Close()
	parent, parentCancel := context.WithTimeout(context.Background(), 300*time.Millisecond)
	defer parentCancel()
	ctx, guard, cancel, err := BindGraphExecution(parent, "spent-receipt", "model")
	if err != nil {
		t.Fatal(err)
	}
	defer cancel()
	wantDeadline, _ := parent.Deadline()
	if deadline, _ := ctx.Deadline(); !deadline.Equal(wantDeadline) {
		t.Fatal("deadline was replenished")
	}
	req, _ := http.NewRequestWithContext(WithModel(ctx, "model"), http.MethodGet, server.URL, nil)
	started := time.Now()
	_, err = (&http.Client{Transport: Transport{}}).Do(req)
	if !errors.Is(err, context.DeadlineExceeded) || time.Since(started) > 2*time.Second {
		t.Fatalf("blocked send did not cancel at deadline: %v", err)
	}
	select {
	case <-arrived:
	default:
		t.Fatal("request never reached local server")
	}
	if sends.Load() != 1 || guard.Reservations() != 1 {
		t.Fatal("blocked send was not counted")
	}
}

func TestGraphExecutionLastAllowedResponseRemainsUsable(t *testing.T) {
	ctx, guard, cancel, err := BindGraphExecution(context.Background(), "spent-receipt", "model")
	if err != nil {
		t.Fatal(err)
	}
	defer cancel()
	for i := 0; i < GraphMaxSends; i++ {
		if err := guard.Reserve(ctx, "model", GraphPhase); err != nil {
			t.Fatal(err)
		}
	}
	if err := guard.Check(ctx); err != nil {
		t.Fatalf("third valid response rejected: %v", err)
	}
}